Need some advice choosing chainrings and cassette please.

[Spiderweb]

Shimano says not:

View attachment 720844

I run 3 bikes with Shimano 105 short cage rear mech, I’ve swapped all the rear cassettes to Ultegra CS6700 12-30t and they work perfectly.

 

[SafetyThird]

some more great replies, thank you very much indeed. All uphill, that sounds like an amazing setup you have and something for me to definitely look at. My brain hurts from all the reading about gearing and compatibility I've been doing this morning.

Currently I see two good options. One is the Shimano r7000 compact 50/34 which I can pickup for £50. If in the future I wanted subcompact gearing I could add the Absolute Black 46/30 rings to that (at a cost of £180). The front derailleur will work if I add a derailleur dropper for £39. Don't need to change anything else on the bike unless I want to go for bigger rear cassette than a 29, in which case I'd near a new rear derailleur.

Alternatively and the one I'm leaning towards, go fully Shimano sub-compact gravel setup as follows.

GRX RX600 10sp in 46/30 - £90
GRX RX400 10sp front derailleur - £27
GRX RX400 10sp rear derailleur - £59
Total £176 plus shipping

The chainset is 2.5mm wider which is why I need the derailleurs but they're not that expensive. However, is that going to be an issue with the chainline? I'm hoping not if I'm using the appropriate derailleurs. It would also mean I could go for larger rear sprockets as the rear derailleur is designed for those. My current 10sp ultegra shifters will work with this system. Looks like a good budget upgrade with standard parts and chainrings easily obtainable in 110 size.

Another thing is that if I want to get the 4iiii power meter at some point, it can be fitted to the 105 crank and the GRX RX810 but they don't show the RX600 on the compatibility list. Need to email them about that.

 

[si_c]

Currently I see two good options. One is the Shimano r7000 compact 50/34 which I can pickup for £50. If in the future I wanted subcompact gearing I could add the Absolute Black 46/30 rings to that (at a cost of £180). The front derailleur will work if I add a derailleur dropper for £39. Don't need to change anything else on the bike unless I want to go for bigger rear cassette than a 29, in which case I'd near a new rear derailleur.

That's a good price for a R7000 crankset.

The chainset is 2.5mm wider which is why I need the derailleurs but they're not that expensive. However, is that going to be an issue with the chainline? I'm hoping not if I'm using the appropriate derailleurs. It would also mean I could go for larger rear sprockets as the rear derailleur is designed for those. My current 10sp ultegra shifters will work with this system. Looks like a good budget upgrade with standard parts and chainrings easily obtainable in 110 size.

I don't know about the chainline but the chainset difference is likely to be because the GRX groupset is designed to work on a 135mm OLD hub from a disc braked bike, so the 2.5mm offset makes sense. I wouldn't expect there to be much of an impact if any, but the only way to find out is either to do it yourself or for someone who already has done so to comment.

Another thing is that if I want to get the 4iiii power meter at some point, it can be fitted to the 105 crank and the GRX RX810 but they don't show the RX600 on the compatibility list. Need to email them about that.

If you get a left side only power meter you can put it onto any HT2 crankset provided the arm length is correct and aside from an aesthetic mismatch there shouldn't be any issue.

 

[Ajax Bay]

You are introducing the 'I might want a power meter' into the discussion which is 'moving the goalposts' and absolutely your prerogative.
Not clear why you need a new RD? By "The chainset is 2.5mm wider" think you mean the chainline. Will have zero noticeable effect on your 105's operation.
The height you can adjust your FD to is an issue with a small 'large' ring, which you've referred to upthread. I assume this from SJS is the dropper (39 quid whooof). Spa Cycles option (@£18) : https://www.spacycles.co.uk/m8b0s106p5161/SPA-CYCLES-Front-Mech-Braze-On-Dropper and it's black
The extra 2.5mm is likely within range of the current (silver) FD - but you can check the lateral reach by unscrewing the upper limit screw and pushing it across by hand (and then returning screw to current position for changes on the turbo).
With all the expense you envisage I wonder if investment in a 20 year old bike is sunk money and you'd be better off with N+1.

 

[fossyant]

Just to add, the smallest chain ring that will fit 110 BCD is a 33, so no changing to a 30. My CX is running 46/34 and a 32 rear. Goes up walls OK.

AB do a 32T in 110, but very costly and oval/wonky

 

[SafetyThird]

Yeah, the 'I might want a power meter in the future' is something I've only really started considering since I found out how much prices have come down in the past decade when the Powertap was the only game in town and I'm currently doing 3 sessions a week on the turbo with Zwift to start rebuilding my fitness. Just found out the GRX600 has a scallop in the back of the crank so you can't fit the 4iiii power meter to it. However, I could just buy a 105 crank arm and swap it out for that if I wanted the power meter.

As to the N+1, that might be a future option if I wanted to really get into some gravel riding but I currently have a Thorn Raven touring bike, a very old Trek 7000 mountain bike and my road bike which is a thing of beauty and quite rare. It's a Titanflex, aluminium monocoque with titanium beam, so it's variable geometry and has suspension. I originally bought it for my journey to Ironman when I lived in the US. I had it set up with a steep geometry, vision flat bar and profile aero bars with bar end shifters. Sadly, on raceday at Ironman New Zealand 2006, the weather didn't play ball and they cancelled the swim and we did just half the bike and half the run. I still have my finishers medal, on the back of which I had 'Unfinished Business' engraved the morning after.

I fully intended to get my ironman but, as is so often the case, life threw a bunch of changes at me in the following years including a move back to the UK, a divorce and a change of careers. Along the way, cycling and triathlon took a back seat and it's only now that I'm starting to want to build some fitness again as I age. The bike though, that's worth keeping and upgrading, it's the most comfortable thing to ride on less than perfect road surfaces.

I put it into road spec and recently had a full bike fit to get it set up so it's comfy and fits me efficiently. A couple of hundred quid getting the gearing sorted out seems like a solid investment in a great bike that has many years still in it.

 

[Alex321]

Shimano says not:

View attachment 720844

You have highlighted the 105 9 speed version, while what he has said before suggests he has the 10 speed version.

 

[SafetyThird]

By "The chainset is 2.5mm wider" think you mean the chainline. Will have zero noticeable effect on your 105's operation.

Ah that's useful to know. When I looked up the spec on the current RD, it says 27T was the largest it could go so figured I'd need a newer one for getting up to say 30T if I went that route.

The height you can adjust your FD to is an issue with a small 'large' ring, which you've referred to upthread. I assume this from SJS is the dropper (39 quid whooof). Spa Cycles option (@£18) : https://www.spacycles.co.uk/m8b0s106p5161/SPA-CYCLES-Front-Mech-Braze-On-Dropper and it's black

Aha, thank you, that's handy to know.

The extra 2.5mm is likely within range of the current (silver) FD - but you can check the lateral reach by unscrewing the upper limit screw and pushing it across by hand (and then returning screw to current position for changes on the turbo).

I'll give that a try.

With all the expense you envisage I wonder if investment in a 20 year old bike is sunk money and you'd be better off with N+1.

See above for explanation.

 

[bobzmyunkle]

GRX RX400 10sp rear derailleur - £59

I think I'm right in saying this won't work with your current shifters. Someone here should be able to advise.

 

[Ajax Bay]

my road bike . . . is a thing of beauty and quite rare. It's a Titanflex, aluminium monocoque with titanium beam, so it's variable geometry and has suspension.

I read (variable geometry, beam suspension" earlier and wondered. What an amazing bike. I can see why you need to go 'all black' with derailleurs and chainset. While you're at it, get some cable under bar 10sp STIs. And some black speedplays.
https://hennessey.uk/ewcc-calendar/2-the-valley-of-the-rocks-200
Square taper would keep it period consistent.
OP: "The bike has early 2000's 105 front and rear derailleurs, an RD 5501 long cage on the back"
This RD (see below) will be completely fine with a 30t large sprocket: it is exactly what I've been running for several years. And as far as capacity is concerned I require 41t of wrapping. The result is that when inadvertently on small/small the chain tells me, and I double shift. Your 'middle option' combo is 16t ring delta plus an 11-30t: zero problem - well within spec.

@Alex321 note the OP is running 10sp and this RD, though part of a 9sp groupset, is entirely compatible with their Ultegra (10sp) STIs.
NB @bobzmyunkle point about GRX compatibility: think this uses Shimano's 11sp shift ratio (1.4) so your 10sp Ultegra STIs won't do.

 

[Ming the Merciless]

Another thing is that if I want to get the 4iiii power meter at some point, it can be fitted to the 105 crank and the GRX RX810

Or XT cranks if you go for an XT triple 46/36/26 Etc.

 

[presta]

You have highlighted the 105 9 speed version, while what he has said before suggests he has the 10 speed version.

The one I highlighted is the part number he quoted. My Deore derailleur does 8 or 9 speed because it's the lever not the RD that differs between speeds, I assumed the 105 would be the same.

I think we all know Shimano always tend to err on the cautious side @presta . Like I said 'Suck it and see'. You'll soon find out.

Well, it's ok buying stuff just to try it out if you have money to throw away when it doesn't work. If there's leeway in hand it'll likely be there to absorb tolerances.

 

[T4tomo]

Alternatively and the one I'm leaning towards, go fully Shimano sub-compact gravel setup as follows.

GRX RX600 10sp in 46/30 - £90
GRX RX400 10sp front derailleur - £27
GRX RX400 10sp rear derailleur - £59
Total £176 plus shipping

The GRX crankset will be fine, not withstanding the 2.5mm offset on the chainline, but GRX 10sp derailleurs have same pull ratios as Tiagra 4700 ("11spd pull ratio") so wont play with your old school 105/Ultegra 10spd shifters. *I'm not certain whether the front derailleur will still work, but the rear certainly wont.

 

[SafetyThird]

Thank you all again, I think I've narrowed this down nicely now. Given that the GRX derailleurs apparently won't play nice with my ultegra shifters, I'll just go with the GRX600 chainset, get a dropper for my current front derailleur and just see how it all works. If the front derailleur works then that's great, if not then I'll revisit getting a more suitable one. The rear sounds as though it should work too for most any cassette up to 30T which should be plenty.

With 46/30 and a 12-30 that gives me 26-100GI and a max 27mph. Honestly, if I'm going 27mph I'll be going down hill and not pedalling

Right time to spend some money. The chainset is out of stock for a couple of weeks but I can source a suitable bottom bracket and install tool and get the dr dropper so I'm ready to go when it arrives, watch this space, I'll report back once it's all done and let you know how I get on.

 

[SafetyThird]

Also just found this which shows it should work although he's on 11sp 105 rather than 10sp. https://www.trainerroad.com/forum/t/shimano-grx-and-cross-compatibility/19369/6